Rotary fractionation apparatus



Dec. 28, 1954 C. H. BowDl-:N ETAI- RoTARY FRACTIONATION APPARATUS Filed March l; 1951 2 Sheets-Sheet l BY-aauu ATTORA Ew'.

Dec. 28, 1954 Q H, BOWDEN ETAL 2,698,287

ROTARY FRACTIONATION APPARATUS Filed March 1.- 1951 2 Sheets-Sheet 2 ATTORNEYS.

2,698,287 Patented Dec. 28, 1954 ihre ROTARY FRACTIONATION APPARATUS Cyril H. Bowden and Edward V. Cooke, Manchester, England, assignors to Imperial Chemical Industries Limited, a corporation of Great Britain Application March 1, 1951, Serial No. 213,384 Claims priority, application Great Britain March 3, 1950 3 Claims. (Cl. 202-158) The present invention is of a device useful for the fractionation of liquids.

According to the invention we provide a device useful for the fractional distillation of liquids comprlsing a cylindrical vessel provided with openings, one at each end, for the entry and exit of vapour, and with a coaxially `rotatable member, said rotatable member be-l ing litted radially with a number of discs, i. e. circular plates or the like structures, which extend to the periphery of the cylindrical vessel, and which have holes in the area". adjacent to the rotating member and said rotating member having also tted thereto al-y ternately, and so in between each pair of the larger discs, a series of unperforated discs which do not extend to the periphery of the said cylindrical vessel.

The rotatable member may be conveniently a shaft. The discs which extend to the periphery of the cylindrical vessel, and which contain an annular hole or annularly arranged holes or perforations in the area adjacent to the member may be composed at least in their central areaand at least in part, of wire gauze which also may contain holes.`

The discs ot' either kind may be attached to the ro tatable member` directly or may be attached by use of spacing collars iitted on the member, which for the purpose is conveniently in the form of a shaft. These spacing collars may, if desired, be shaped in order to cause the ow of vapour, as it turns from a radial direction inwards to a radial direction outwards, to be free from eddies.y

The device isfto be understood as for use with the laxis of the cylindrical vessel horizontal, or approximatey so.

Optionally, in what, in such a position, can be referred to as the bottom of the cylindrical vessel, i. e. the trough-like, lower part, there may be, between each pair of said rotatable discs, plates in the form of segments of circles with the chord horizontal, attached to theperipheryof the cylindrical vessel so as to hold in the vessel a constant volume of liquid. This total volume is preferably diminished as much as possible; hence, these plates are advantageously of substantial thickness so as to minimise as indicated the amount of liquid held in the cylindrical vessel during a fractional distillation operation and retained at the end thereof. Also with minimum amount of liquid there is better fractionation because each pool is agitated more thoroughly.

These segment-like plates are conveniently of such a height measured from the bottom to the chord that the line of the chords intercepts the circles which represent the peripheries of the unperforated discs, the aim being to provide a meandering passage for vapour, which passes along barriers the surfaces of which are wet with liquid.

The device, as will be understood, is connected at the one end with a boiler, and at the other end with a condenser, as necessary via a dephlegmator. It wlll be understood that these connections may be of any desired and appropriate form and shape and thatvthe one housing may be such as to provide for dispensing with, or reducing to a minimum, connecting pipes, llanges and such like l'itments.

Such a device is adapted to batchwise distillation; for continuous distillation purposes appropriate inlets and outlets provided with valves are made in the wall at the bottom of the cylindrical vessel so that liquid may be fed into or removed from any compartment of the trough-like portion. v

The accompanying drawing Fig. l, illustrates a crosssection of a particular form of the device. Figure 2 is a transverse sectional view of a modification of the device shown in Figure l and Figure 3 is a longitudinal cross-sectional View of a portion of the device of Figure 2 taken on the lines 3-3 in Figure 2. In the drawing a is one of a series of perforated discs which extend to the periphery of the vessel, b is one of a series of non-.erforated discs which do not extend to the periphery of the vessel, c is one of a series of segment-like plates attached to the lowermost portion of the periphery of the vessel, d is the casing of the cylindrical vessel, e is a rotatable shaft to which the discs are attached, f is an opening whereby vapours from a boiling vessel may enter the cylindrical vessel, gis an opening whereby the vapours passing through the device may leave the vessel, h is a pipe whereby part of the liquid condensed from the vapours leaving the vessel may be returned to the vessel, i is a gland, j is a bearing, and kk represents the level of the liquid retained in the Vessel when it is being used for fractionating a liquid.

The means of attaching the discs b to the rotating member and of attaching the segment-like plates c to the periphery of the vessel are such that liquid tight unions are provided.

In the operation of the particular form of the device as illustrated in Fig. l, the rotatable member is rotated slowly, the vapours from the liquid to be fractionated are passed into the vessel through the opening f, the vapours pass through the device in the manner indicated by the dotted line zz, leaving the vessel through the opening g, and pass into a condenser via a dephlegmator of any conventional type, so arranged that a portion of the condenser liquid is returned to the vessel through the pipe h. When the device has been operating in this way for a short time, the level of the liquid in the vessel rises to that indicated by the dotted line kk, and, thereafter, liquid passes out of the vessel through the opening f at a rate approximating to the rate at which it is returned to the vessel through the pipe h.

The segment-like plates (c) may be inserted and fixed in various ways, apparent to any person skilled in the engineering art. By way of indication it will be said that an arc-like recess may be provided in the wall of the cylinder into which the plates suitably provided with spacing blocks may be packed synchronously with the insertion of the rotatable member, carrymg the discs, into the cylinder. Or the cylinder may be provided, along its bottom, with a projecting gully or channel of suitable shape into which the segmentlike plates, each provided with an ear to correspond, and with spacing blocks, may be packed and fixed by screws. Such a constructional arrangement is shown in Figs. 2 and 3.

Any suitable materials may be used in the construction of the device. It will be understood that for many purposes some form of what is colloquially known as stainless steel is a very suitable material.

The surfaces of the discs may advantageously be made rough or irregular so as to increase the area of wettable surface and to promote turbulence in the vapour stream passing near it. A convenient method of so modifying the surface is to cut, by means of a lathe, a spiral groove thereon.

By way of example, to illustrate working of the dcvice the figures below are given. These relate to a particular embodiment of the invention in which the cylindrical vessel is 8 in internal diameter and contains 25 discs of each kind, so, in all, 50 discs spaced apart.

Operated under conditions of total reflux with a mixture of o-xylene and p-xylene under a pressure of 400 mm. mercury, the composition of the liquid ,at the two ends corresponds with the separation equivalent to 7.6 transfer units as calculated according to the directions given by Walker, Lewis, McAdams and Gilliland in Principles of Chemical Engineering, 3rd edition, New York, 1937, on page 490, and also by Chilton andv Colburn inv Industrialandl Engineering Chem-- istry, 1935, 27, at page 255. The separation thus indicated is substantially independent of rate of throughput. The. pressure. dilerence' between the ends. varies: according to rate of through-put. It.is:.0.023;-mrn. merr cury, ati4l lb; per. hour through-put, andz2i7' mm.. mercury. at .3'5 lb. per hour through-put;Y

In'. another embodiment of, the'. invention,v with the discs'. Vi apart butt otherwise as.A described'. above a separation. oft. o-Xylene. from p-xylenel representedi by. 5.6; transfer units is obtained. Intthis embodiment:pres-y sure, drop varies as: the squareof the mass'through-.put and inversely as; theso-called.Y absolute`4 pressure,. asY is` shown inV this table:

Abs. pres- Pressure. Throughout sure, mm. Drop, mm. rate, lb. per Hg i H hour For comparison a vertical column, packed with 1/2. or 1l Raschig rings, and of a height to. provide an equivalent number of transfer unitshas, at 7601 mm. of. mercury absolute pressure a pressure drop of 2Ov or 14mm. of-mercury just below thek oodingpoint, and of 5 mm. or 3 mm. of mercury at the minimum value of pressure. drop per transfer unit' at low rateV is a low lpressure drop and a low liquidhold-up. As-

compared with other fractionating devices, itsefciency is high especially at low rates of lthrough-put. accordingly be used to advantage in fractionaldistillation of liquids at low pressure, e. g. at pressures-often millimetres of mercury or below.

The device is useful also in two-phase vcounter current operations other than those of fractional distillation. That is tosay it can, be used 4for treating gas:with'y liquid or-vice versa .or in the extraction. of one liquid with another in which' it is immiscible.

We claim:

1. A fractional distillation device in which4 vapors from .a boiling mixture ofv liquids are fedinto th'edevice, vapors emerging from the device are condensed' and a portion of the condensate is returned to the device as reflux and the uncondensed vapors withdrawn from the device which comprises, an, approximately horizontally positioned closed cylindrical.` vessel` havingJ anoutwardly extending recess in its lowermost portion, said vessel being. provided with an. entryport at one It can end thereof for supplying vapors to the cylindrical vessel; anexit portV on-the upper sideofthe opposite end thereof through which thefuncondensed vapors can be withdrawn, means for returning condensate to said vessel on the same end of said vessel as said exit port, and means for withdrawing condensate from the same end of said vessel as said inlet port, a rotatable member along the centrallongitudinal axis of the vessel, said member having aplurality of discs attached-thereto, alternate discs being'of the same diameter as the internal diameter of. the vessel' and extend to the periphery of the cylindrical vessel exceptV in the' area of the recessed portiony and, being perforated in the area adjacent to the rotatable member so that the vapor passing'through said vessel'is forced through said ccntrally located perforations, the other discs being of sucient diametei to-extend beyond said centrally located perforations but smaller than the internal diameterofthe vessel so that the vapor supplied-'to'said cylindrical vessel traverses said vessel-longitudinally in a meandering path which leads backy andt'orth between thevspace between the vessel wall andthe smallei'f'discs andk the centrally locatedv perforations in the largerv discs, said vesselbeing provided with a plurality of longitudinally/ spaced segmental partitions in-'its lowermost portion which divider the outwardlyv extending lowermost portion of said vessel intov a plurality of longitudinally spaced liquid-tight receptacles into which' saidvdiscs dip so -that the returned condensate is longitudinally. connedinvsaid'receptacles whereby said discs as they, are rotated by; said rotatable memberl deposit the liquidv condensed thereon in said receptacles and'y pick up fresh liquid-'whichis enriched in thelowcr boil1ngcomponents of the mixturewofy liquids` fed to the. device, said lsegmental 'partitions 4and `said outwardy\ extending lowermost i portion of said vessel functioningto enable returnedy condensateto successively overflow-said'partitions andllow past said larger discsto'y longitudinally traverse said lowermost portion of said vessel 1n a direction counter-current to` the-.passage'cfy vapor through said vessel while being temporarily rctained-in eachsucceedingreceptacle where' the lower boilingcomponents of said-'condensaterare progressively removed.

2. .A-tractionali-distillation device 4as recited inlclai'rnf 1 in which said lmeans for returning condensatetosaid vessel comprises a second inletI port.y

3. A fractional distillation device as recited in' claim 2 1n which the surfaces of the-discs are` rough'ened;

References Cited in the tile of this patent UNITED STATES PATENTS' Number Name Date 447,258 PattenlFcb'. 24,* 1891' 701,6191 Riecke June '3,j 1902 1,838,009. Strecker vDec;v 22, 193'1 FOREIGN PATENTS Number Country;l Date'-4 5,/113 Great 'Britain of 1895 456 i DenmarkA Mar.'l4, 1896r 201,568v Germany,y Sept. 27, 1906` 269,790y GreatBritain' Apr. 28,' 1927 121,098 Switzerland June f 16,- 1927r 41,697 Denmark Feb. 23, 1928 408,016 Great Britain- Apr. 5, 1934 

1. A FRACTIONAL DISTILLATION DEVICE IN WHICH VAPORS FROM A BOILING MIXTURE OF LIQUIDS ARE FED INTO THE DEVICE, VAPORS EMERGING FROM THE DEVICE ARE CONDENSED AND A PORTION OF THE CONDENSATE IS RETURNED TO THE DEVICE AS REFLUX AND THE UNCONDENSED VAPORS WITHDRAWN FROM THE DEVICE WHICH COMPRISES, AN APPROXIMATELY HORIZONTALLY POSITIONED CLOSED CYLINDRICAL VESSEL HAVING AN OUTWARDLY EXTENDING RECESS IN ITS LOWERMOST PORTION, SAID VESSEL BEING PROVIDED WITH AN ENTRY PORT AT ONE END THEREOF FOR SUPPLYING VAPORS TO THE CYLINDRICAL VESSEL, AN EXIT PORT ON THE UPPER SIDE OF THE OPPOSITE END THEREOF THROUGH WHICH THE UNCONDENSED VAPORS CAN BE WITHDRAWN, MEANS FOR RETURNING CONDENSATE TO SAID VESSEL ON THE SAME END OF SAID VESSEL AS SAID EXIT PORT. AND MEANS FOR WITHDRAWING CONDENSATE FROM THE SAME END OF SAID VESSEL AS SAID INLET PORT, A ROTATABLE MEMBER ALONG THE CENTRAL LONGITUDINAL AXIS OF THE VESSEL, SAID MEMBER HAVING A PLURALITY OF DISCS ATTACHED THERETO, ALTERNATE DISCS BEING OF THE SAME DIAMETER AS THE INTERNAL DIAMETER OF THE VESSEL AND EXTEND TO THE PERIPHERY OF THE CYLINDRICAL VESSEL EXCEPT IN THE AREA OF THE RECESSED PORTION AND BEING PERFORATED IN THE AREA ADJACENT TO THE ROTATABLE MEMBER SO THAT THE VAPOR PASSING THROUGH SAID VESSEL IS FORCED THROUGH SAID CENTRALLY LOCATED PERFORATIONS, THE OTHER DISCS BEING OF SUFFICIENT DIAMETER TO EXTEND BEYOND SAID CENTRALLY LOCATED PERFORATIONS BUT SMALLER THAN THE INTERNAL DIAMETER OF THE VESSEL SO THAT THE VAPOR SUPPLIED TO SAID CYLINDRICAL VESSEL TRAVERSES SAID VESSEL LONGITUDINALLY IN A MEANDERING PATH WHICH LEADS BACK AND FORTH BETWEEN THE SPACE BETWEEN THE VESSEL WALL AND THE SMALLER DISCS AND THE CENTRALLY LOCATED PERFORATIONS IN THE LARGER DISCS, SAID VESSEL BEING PROVIDED WITH A PLURALITY OF LONGITUDINALLY SPACED SEGMENTAL PARTITIONS IN ITS LOWERMOST PORTION WHICH DIVIDE THE OUTWARDLY EXTENDING LOWERMOST PORTION OF SAID VESSEL INTO A PLURALITY OF LONGITUDINALLY SPACED LIQUID-TIGHT RECEPTACLES INTO WHICH SAID DISCS DIP SO THAT THE RETURNED CONDENSATE IS LONGITUDINALLY CONFINED IN SAID RECEPTACLES WHEREBY SAID DISCS AS THEY ARE ROTATED BY SAID ROTATABLE MEMBER DEPOSIT THE LIQUID CONDENSED THEREON IN SAID RECEPTACLES AND PICK UP FRESH LIQUID WHICH IS ENRICHED IN THE LOWER BOILING COMPONENTS OF THE MIXTURE OF LIQUIDS FED TO THE DEVICE, SAID SEGMENTAL PARTITIONS AND SAID OUTWARDLY EXTENDING LOWERMOST PORTION OF SAID VESSEL FUNCTIONING TO ENABLE RETURNED CONDENSATE TO SUCCESSIVELY OVERFLOW SAID PARTITIONS AND FLOW PAST SAID LARGER DISCS TO LONGITUDINALLY TRAVERSE SAID LOWERMOST PORTION OF SAID VESSEL IN A DIRECTION COUNTER-CURRENT TO THE PASSAGE OF VAPOR THROUGH SAID VESSEL WHILE BEING TEMPORARILY RETAINED IN EACH SUCCEEDING RECEPTACLE WHERE THE LOWER BOILING COMPONENTS OF SAID CONDENSATE ARE PROGRESSIVELY REMOVED. 